Message 77418 - Python tracker

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Author	vstinner
Recipients	belopolsky, drj, mark.dickinson, vstinner
Date	2008-12-09.14:59:57
SpamBayes Score	7.807461e-05
Marked as misclassified	No
Message-id	<1228834799.19.0.954122480352.issue3166@psf.upfronthosting.co.za>
In-reply-to

Content
Ok, I understand why different versions of the same code gives different results: compiler flags! Python 2.5.1 is my Ubuntu version (should be compiled with -O3) whereas Python 2.7 and 3.1a0 are compiled by me with -00. Results with Python 2.5.1: - with -O0, float(295147905179352891391L) gives 2.9514790517935283e+20 - with -O1, float(295147905179352891391L) gives 2.9514790517935289e+20 I'm unable to isolate the exact compiler flag which changes the result. I tried all options listed in the gcc doc for the -O1 option: http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Optimize-Options.html#Optimize-Options

Ok, I understand why different versions of the same code gives 
different results: compiler flags! Python 2.5.1 is my Ubuntu version 
(should be compiled with -O3) whereas Python 2.7 and 3.1a0 are 
compiled by me with -00.

Results with Python 2.5.1:
 - with -O0, float(295147905179352891391L) gives 
2.9514790517935283e+20
 - with -O1, float(295147905179352891391L) gives 
2.9514790517935289e+20

I'm unable to isolate the exact compiler flag which changes the 
result. I tried all options listed in the gcc doc for the -O1 option:
http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Optimize-Options.html#Optimize-Options

History
Date	User	Action	Args
2008-12-09 14:59:59	vstinner	set	recipients: + vstinner, mark.dickinson, belopolsky, drj
2008-12-09 14:59:59	vstinner	set	messageid: <1228834799.19.0.954122480352.issue3166@psf.upfronthosting.co.za>
2008-12-09 14:59:58	vstinner	link	issue3166 messages
2008-12-09 14:59:57	vstinner	create